It's not quite an ad block, so let's call it an ad pause: The latest version of the Windows Edge browser, available in Windows 10 build 14316, selectively pauses Flash content that does not appear central to the content.
Microsoft released the update to Windows Insider, stating that the changes were made to prolong battery life, performance, while continuing to let Flash-based videos and games run normally.
But the Edge team also said that while Flash has been integral to the web's development, it's time to move on:
We encourage the web community to continue the transition away from Flash and towards open web standards. Standards like Encrypted Media Extensions, Media Source Extensions, Canvas, Web Audio, and RTC offer a rich way to deliver similar experiences with increased performance and security. We will continue to work within the W3C to ensure standards unblock all developers to fully transition away from Flash.
We’re aligned with other browsers in this transition from Flash towards a modern standards-based web. Over time, we will provide users additional control over the use of Flash (including content central to the page) and monitor the prevalence of Flash on the web. We are planning for and look forward to a future where Flash is no longer necessary as a default experience in Microsoft Edge.
More details on the move are at Windows Super Site, and look for the feature to appear in general availability with Windows 10 Anniversary Update this summer.